High-Speed Cryogenic Optical Connector for Focal Plane Array Read-out

A cryogenic optical link is proposed for development that uses a VCSEL-based micro transmitter placed inside the cryostat, and transmitting through a dewar window to a detector-based micro receiver placed outside the dewar. Interconnection to focal plane readout circuit is proposed using an application specific integrated circuit to receive the read out data and electrically drive the VCSEL to transmit the data. The micro transmitter and micro receiver include integrated lens for collimation and high alignment tolerance. In order to overcome reliability and detuning problems faced by commercial off the shelf oxide VCSELs, a lithographic oxide-free VCSEL is proposed for the cryogenic laser. Scaling to single data channel speed to > 50 Gbps is proposed due to compact packaging and short lead lengths of the micro optical components. Scaling to high channel count is also possible using single mode VCSEL arrays for wide alignment tolerances of VCSEL and detector arrays.